Harmful Algae Blooms

What is a blue-green algae bloom?

Algae are plant-like organisms that thrive in water. Blue-green algae or cyanobacteria are actually bacteria naturally found on land and in water bodies. Under certain conditions—such as an excess of nitrogen and phosphorus, warm water, and calm weather—they can multiply rapidly, causing "blooms." These blooms usually float to the surface and can be several inches thick near the shoreline. They often look like blue-green paint was spilled on the water's surface, but can also look bluish, brownish, or reddish green. Algae can be present year-round, and not all blooms are harmful.

Most lakes will naturally have an occasional algae bloom. Temperature, wind and sunlight play a role in the formation of blooms. An excess of nutrients, particularly phosphorus, can increase the frequency and severity of algae blooms. Frequent algae blooms can be a sign of declining water quality.

Harmful algae blooms (HABs)

Harmful algal blooms (HABs) happen when algae grow uncontrollably. These blooms can occur in both freshwater environments, like lakes and rivers, and saltwater environments, such as oceans and bays. 

Most blue-green algae blooms do not present a health risk. However, some can produce toxins that are harmful to people, fish, shellfish, marine mammals, birds, and pets. This can be especially dangerous if any of the water containing the toxins is swallowed. People and animals can also get exposed through skin contact during swimming, breathing in small airborne droplets that contain toxins or eating food or supplements containing toxins.

Freshwater HABs

In freshwater settings, harmful algal blooms are typically caused by blue-green algae or cyanobacteria. Freshwater and marine HABs are usually distinct, but they can overlap in low salinity estuaries where rivers meet the sea, such as Terrell Creek in Birch Bay.

Marine or Saltwater HABs

In saltwater, algae that produce toxins can make both humans and animals sick. Exposure can occur through eating contaminated seafood, swimming in affected water, or inhaling sea spray containing these toxins. Symptoms of exposure can range from mild to life-threatening, depending on the type and amount of toxin involved. An example of a marine HAB is a red tide, caused by zooplankton that consume algae producing a red pigment and various toxins.

What do I do if I see a blue-green algae bloom?

Algae blooms can be patchy, move to other parts of the lake and change with time. When in doubt, follow these guidelines when you see an algae bloom:

  1. Do not swim or water ski in areas where algal scum has accumulated.
  2. Do not drink lake water.
  3. Keep kids, pets and livestock away from areas where a visible bloom is present.
  4. Clean fish well and discard entrails – do not feed them to your pets.
  5. When in doubt, stay out!

If you see a blue-green algae bloom that can be tested from an area that is publicly accessible, please contact us at 360-778-6000 or [email protected]  to report it. Once a bloom has been reported, WCHCS will visit the site and determine whether sampling is necessary. If a sample is taken and the lab results show that a bloom is toxic, we will post appropriate signage and send notifications to the community of potential health concerns.  

We can only test if the area with the bloom is within a general public access area. If you see a blue-green algae bloom adjacent to private property, call our office or visit www.nwtoxicalgae.org to obtain sampling instructions.

Testing does not ensure that all areas of a lake are safe. 

What are the signs of toxic algae poisoning?

Blue-green algae can produce nerve toxins (neurotoxins) and liver toxins (hepatotoxins). Signs of neurotoxin poisoning include numbness, tingling and dizziness in humans. In animals, symptoms can include weakness, staggering, difficulty breathing, convulsions and death. Signs of hepatotoxin poisoning include abdominal pain, diarrhea and vomiting in humans and death in animals. Call your doctor or veterinarian right away if you or your pets have signs of poisoning.

Can I eat fish from the lake when a toxic bloom is present?

Toxins can accumulate in fish tissues, especially in the liver, kidneys and other organs. Before eating, remove internal organs, which may contain more of the toxin.

Is it safe to drink water from the lake during a bloom?

No, do not use this water as a drinking source, even if using a filter. A water filter or purifier will not remove the toxins. 

What can I do to help prevent toxic algae?

The best way to help prevent future toxic algae blooms at your lake is to reduce phosphorus coming into the lake. This includes: 

  • Avoiding fertilizers for your lawn or using phosphorous-free fertilizer 
  • Clean up pet waste immediately.
  • Scheduling a routine septic system inspection. 
  • Re-establishing shoreline vegetation by replacing lawn with native plants. 
  • Wash your car at a commercial car wash or on your grass lawn to prevent runoff directly into the lake.

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Contact Us

Phone: 360-778-6000

Email: [email protected]